KR20020054330A - Blind fastener and drive nut assembly - Google Patents

Abstract

A blind fastener 10 with an improved drive nut 50 has been described. The fastener includes a screw 20, a sleeve 30, a nut 40 and a drive nut 50. The improved drive nut of the present invention has a protruding nip 56 that exactly matches the drive groove 46 located in the nut head 44. Once the blind nut fasteners are assembled, the drive nut 50 will mate with the nut 40 head to prevent any relative rotation.

Description

Blind Fasteners and Drive Nut Assemblies {BLIND FASTENER AND DRIVE NUT ASSEMBLY}

Blind fasteners are commonly used to hold two sheets together when there is no other way to approach the bottom face (blind face) of one of the sheets. Such fasteners are widely used in aircraft and spacecraft assembly. Due to the vibration and acoustical fatigue experienced in these environments, it is necessary to create fasteners with the strength and reliability to withstand.

Conventional blind fasteners improved by the present invention include (1) screws, (2) sleeves, (3) nuts, and (4) drive nuts. Examples of conventional blind fasteners are described in US Pat. Nos. 4,772,167 and 4,747,202. Generally, the screws each have a threaded sleeve, a nut therein and a threaded face on the outside to allow the drive nut to be positioned on the screw. The blind fasteners are inserted into the aligned holes of the sheets that are fastened together, and after the installation is complete the sleeve and the nuts will fasten the sheets together.

The screw has the shape of a long threaded bolt with an enlarged head at one end of the screw, and at the opposite end of the head there are two machined flats. The machined flats are a wrenching surface that allows the tool to rotate the screw during assembly and installation of the blind fasteners. The screw also has a frangible groove in a predetermined position on the threaded section machined to a diameter smaller than the short diameter of the outer thread. The purpose of this soft groove is to prevent over torque and / or excessive upset of the sleeve during installation by acting as a breakneck. When any mounting load is achieved, the soft grooves first fail at the torsion shear and then fall off the assembly to prevent overloading.

The sleeve has a cylindrical shape and is made of a flexible material. The purpose of the sleeve is to radially expand during installation and to abut the blind face of the seat. The nut has a cylindrical shape and resembles a flush head or protruding head bolt, with the exception that the nut is internally threaded throughout and a drive groove on top of the head. Moreover, the nut has a recess formed around its diameter to provide friction on the screw to prevent the screw from loosening once the fastener is installed.

The drive nut resembles a conventional hexagon nut and has the same internal stillbirth as the nut. At one end of the drive nut there is a chamfrerd angle starting from the outer hexagon and ending at a predetermined counterbore larger than the internal thread diameter. Moreover, the drive nut has an annular ridge made of a flexible material that causes the annular ridge to deform into the head and groove of the nut.

A conventional process of assembling blind fasteners consists of placing the thread on the screw until the sleeve abuts the head of the screw and then threading on the screw until the nut rests on the sleeve. The nut is then recessed on the outer wall by a physical deformation process that places a portion of the nut material with respect to the inner thread to prevent loosening. The drive nut is then threaded onto the screw until it rests against the head of the nut. The installation process of the blind fastener is accomplished by keeping the drive nut stationary and at the same time using a tool suitable for fitting onto the machined flats on the screw. The tool prevents the drive nut from rotating and simultaneously rotates the screw. As the screw rotates, the sleeve is pulled toward the blind side of the sheet material. The flexible sleeve then abuts the sheet material and begins to deform into the expanded diameter. On the other hand, at the opposite end of the blind fastener assembly, the annular ridge of the drive nut is deformed and begins to flatten with respect to the nut head. As the torsional and compressive loads increase, the annular ridge of the deformable drive nut begins to rotate 180 degrees before penetrating the groove of the head of the nut, which is evidenced by head marking and material damage.

The drive nut acts as a "jam nut" by forcing it against the nut head to prevent the nut from rotating. In some torsional and compressive loads, the screw stops rotating and the soft groove of the crushed wood breaks, causing the drive nut and the remaining screws to stay away from each other.

The problem with conventional blind fasteners is derived from the deformable drive nut. Optimal installation performance and reliability are not achieved from blind fasteners, since the deformable drive nut allows undesired rotation and "jam nut effect". The deformable drive nut rotates on the head of the nut when the annular ridge of the drive nut deforms into the groove of the nut head. This deformation process causes the nut to rotate and the nut head to be damaged or scratched. This result is not only visually obvious, but can also degrade the corrosion resistance of the nut and damage the plating under the head and grip area of the nut. Finally, the "jam nut effect" of the deformable drive nut causes a large change in the required installation load. This can result in premature screw breakage, and can also result in a positive inconsistency of the sleeve material deforming to an expanded diameter, thus degrading the integrity of the blind fasteners.

Accordingly, there is a need for a blind fastener with an undeformable drive nut that securely engages into the head of the nut, eliminating all problems associated with the rotation and unwanted rotation of the nut and the "jam nut effect".

FIELD OF THE INVENTION The present invention relates to blind fasteners that hold panels and sheet materials together, and more particularly to improved drive nut assemblies.

1 is a partial side cross-sectional view of the blind fastener system of the present invention.

FIG. 2 is a partial side cross-sectional view of the blind fastener system of FIG. 1 showing a drive nut engaged in a drive groove of the nut. FIG.

3 is a partial side cross-sectional view of the blind system of FIG. 1 showing the blind fasteners after assembly is complete.

4 is a partial side cross-sectional view of the blind fastener system of FIG. 1 showing the blind fastener during installation in a pair of sheets.

FIG. 5 is a partial side cross-sectional view of the blind fastener system of FIG. 1 showing the blind fastener during installation in a pair of sheets and showing that the deformable sleeve is deformed.

6 is a partial side cross-sectional view of the blind system of FIG. 1 showing the blind fasteners after installation is complete.

FIG. 7A is a top view of the nut of the blind fastener system of FIG. 1 showing a drive groove in a cross slot configuration. FIG.

FIG. 7B is a partial side cross-sectional view of the nut of FIG. 7A. FIG.

8A is a top view of the nut of the blind fastener system of FIG. 1 showing a drive groove in a single slot configuration.

8B is a partial side cross-sectional view of the nut of FIG. 8A.

9A is a perspective view of the drive nut of the blind fastener system of FIG. 1 showing four nibs with inclined mating surfaces.

9B is a perspective view of the drive nut of the blind fastener system of FIG. 1 showing four nips with flat mating surfaces.

10A is a perspective view of the drive nut of the blind fastener system of FIG. 1 showing two nips with inclined engagement surfaces.

10B is a perspective view of the drive nut of the blind fastener system of FIG. 1 showing two nips with flat mating surfaces.

The present invention relates to a blind fastener with an improved drive nut and an assembly process. The blind fasteners of the present invention include screws, sleeves, nuts and drive nuts. The screws, sleeves and nuts of this blind fastener are similar to those of the conventional blind fasteners discussed above. The development of the invention relates to a new construction of the drive nut and a new assembly process for the blind fasteners. The new drive nut and assembly process significantly improves the reliability of the blind fasteners by eliminating the inconsistencies associated with forcing the drive nut into the head of the nut.

The new drive nut of the present invention has a protruding nip that matches exactly with the groove located within the nut head. The protruding nip of the new drive nut is not deformable and serves to replace the deformable annular ridges used in conventional drive nut assemblies. The configuration of the grooves in the protruding nip and the nut head can take many forms, as long as they can be mated with each other. The protruding nip is assembled to one end of the drive nut and is fully engaged to resist any installation torsional load. Once the new assembly process for the blind fastener is completed, the drive nut will mate with the nut head to prevent any rotation of the nut during installation of the blind fastener in the seat to be secured.

The process of assembling the blind fastener with the new drive nut is also different from the process used conventionally. The assembly process will now include positioning the sleeve in a position adjacent the screw head above the thread of the screw. The nut is then partially screwed onto the screw until the internal threads in the area of the enlarged nut head are not fully screwed onto the screw. The protruding nip of the new drive nut is then aligned and physically engaged into a mating groove in the nut head. The mated drive nut and nut are then rotated, as a result of which the drive nut and the nut are physically locked together and screwed onto the screw as a single unit. Once the nut is adjacent to the sleeve, assembly is completed by positioning the screw, sleeve, nut and drive nut so that the nut can be concave. The recess forming process places a small physical strain on the outer surface of the nut, which causes a small amount of nut material to move against the inner thread, causing sufficient friction to prevent loosening.

Once the new assembly process is complete, blind fasteners with new drive nuts are installed in the seat and secured by means similar to those used in conventional blind fasteners. That is, a tool with means for keeping the drive nut stationary and at the same time rotating the screw is used to cause the sleeve to deform with respect to the blind side of the seat and to fix the seat between the nut and the sleeve.

When the sleeve deforms against the blind side of the seat during installation, the drive nut will not deform into the nut head. The mating connection between the drive nut and the nut head prevents damage and scratching of the nut head and preserves corrosion resistance. Unlike conventional drive nuts with deformable annular ridges, the drive nuts of the present invention do not have a "jam nut effect". The protruding nip on the drive nut eliminates the unpredictability of the installation load imposed on the screw by not forcibly deforming the nut head. This, in turn, greatly reduces the risk of premature screw breakage and increases the consistency of the amount of sleeve material to be deformed with respect to the seat.

Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

The invention is practiced in blind fasteners 10 that are used to join two or more panels or sheet materials together. Typically, the sheets are made of materials or other composite materials commonly used in the aviation industry, including aluminum. As shown in FIG. 4, the blind fastener 10 is designed to hold the sheets 12, 14 together by generating a clamping force. The blind fastener 10 is particularly useful for the assembly of aircraft and spacecraft in which the seat 14 is inaccessible or inaccessible to the “blind” surface 18.

Referring to FIG. 1, the blind fastener 10 includes a screw 20, a sleeve 30, a nut 40, and a drive nut 50. Generally, the screw 20 has an outer thread 22 that allows the sleeve 30, the nut 40 and the drive nut 50 to be positioned on the screw 20. In this regard, the blind fasteners 10 are assembled and installed in the seats 12, 14, the sheets 12, 14 each having holes of a diameter large enough to allow the installation of the blind fasteners 10 into the seats. Have

The screw 20 has the shape of an elongated threaded bolt with an external thread 22 and an enlarged head 24. At the opposite end of the enlarged head 24 there are two machined flats 26, which engage a drive tool (not shown) with the machined flats 26 and torque them. To provide a wrenching surface that allows to generate a rotational movement of the screw 20. In a preferred embodiment, the enlarged screw head 24 is sized to have a diameter that matches the diameter of the sleeve 30 measured from the outer surface of the sleeve body 32.

The nut and the drive nut are each threaded inside and have the same internal thread 33. The inner thread 33 is sized to thread-engage cooperating with the outer thread 22 of the screw 20. This allows the nut and drive nut to be positioned above the screw 20.

The screw 20 also includes a frangible groove 28. The soft groove 28 is located at a predetermined position on the threaded portion of the screw 20 and is machined to a diameter smaller than the minor diameter of the outer thread 22. The soft groove 28 acts as a breakneck that will fail at the torsional shear and break out of the blind fastener 10 when any torsional load is achieved. This breaking neck function of the soft groove 28 prevents excessive torque and / or upset of the sleeve during installation. In a preferred embodiment, the soft groove 28 is machined in the axial position of the screw 20 such that the remainder of the screw 20 extending from the head 24 when the soft groove 28 is broken is the nut head ( It will be substantially coplanar with the top surface 43 of 44.

The sleeve 30 has a cylindrical shape and is made of a flexible material. The sleeve 30 is positioned on the screw 20 until the sleeve 30 engages with the screw head 24. The sleeve face 36 is designed to deform when the screw 20 is rotated and the nut 40 is dragged toward the sleeve 30. The tapered nose 42 of the nut 40 presses the inner diameter of the sleeve face 37 by force, causing the inner diameter 37 to expand radially and ultimately as the sleeve body slides over the tapered nose 42. Bend to Continued application of the load increases the diameter of the sleeve body 32 and adjoins the blind inner surface 18 of the seat 14, thereby providing a seat 12, between the sleeve 30 and the head 44 of the nut 40. 14) together.

The nut 40 has a cylindrical shape and preferably resembles a countersunk head bolt. The nut 40 includes a nut body 41, a tapered nose 42 located at one end of the nut body, and a nut head 44 located at an end opposite to the tapered nose 42. The nut body 41 preferably has an outer diameter substantially the same as the outer diameter of the sleeve body 32. The tapered nose 42 protrudes inward and has a diameter smaller than the diameter of the nut body 41. The tapered nose 42 abuts the sleeve inner diameter 37 when on the screw 20. As shown in FIG. 2, the nut head 44 includes a drive groove 46 that allows the drive nut 50 to be engaged with the nut 40.

As shown in FIGS. 7A and 7B, the drive groove 46 of the nut head 44 has a plurality of bends 48. The bend 48 in the drive groove 46 allows the nut head 44 and the drive nut 50 to be mated so that rotation of the nut 40 and the drive nut 50 during installation of the blind fastener 10 is achieved. It can be formed in any configuration that prevents it. In the preferred embodiment, as shown in FIG. 7A, the bend 48 is in a cross slot configuration, so the drive nut 50 must have a protruding nib 56 in the cross slot configuration. The bend 48 of the drive groove 46 may alternatively have a single slot configuration as shown in FIGS. 8A and 8B, or as long as the nip 56 of the drive nut 50 has a mating configuration It can have any other configuration, such as the shape of.

As shown in FIGS. 9A and 9B, the drive nut 50 preferably has the shape of a conventional hexagon nut and has the same internal thread 33 as the nut 40. The drive nut 50 has an outer surface 52 for engagement by a drive tool (not shown) that prevents rotation of the drive nut. The drive nut 50 has a plurality of protruding nips 56 that provide a smooth mechanical engagement with the nut head 44. As above, the nip 56 is configured to precisely match the bends 48 that make up the drive groove 46 of the nut head.

Nip 56 is made of a non-deformable material so that nip 56 will not deform during installation of the blind fasteners. As with the bend 48 of the nut 40, the number of nips 56 on the drive nut 50 can vary and can be of many different geometries and shapes. In a preferred embodiment, as shown in FIGS. 9A and 9B, four nips 56 are present on the drive nut and each nip has a rectangular shape with a mating surface 57 and a driving surface 58. In FIG. 9A, the engagement surface 57 is inclined relative to the drive surface 58, and in FIG. 9B the engagement surface 57 is flat. Also, as shown in FIGS. 10A and 10B, the drive nut 50 may be formed of two nips 56, having an inclined engagement surface as shown in FIG. 10A, or flat as shown in FIG. 10B. Has a mating surface. Preferably, the nip 56 protrudes from the drive nut face 54 to form a rectangle having a length equal to the distance between the outer face 52 and the inner thread 33.

Before installing the blind fasteners 10 in the seats 12, 14, the blind fasteners are assembled. 1 to 3, the assembly process is a series of steps that result in the sleeve 30 being positioned over the screw and nut 40 and the drive nut 50 threaded over the screw 20. Include them. First, as shown in FIG. 1, the sleeve 30 is positioned above the outer thread 22 until the sleeve end 34 is adjacent to the screw head 24. The nut 40 is then partially screwed onto the screw 20, and the tapered nose 42 faces the sleeve face 36 and the inner diameter 37. The nut 40 is preferably threaded over the screw until the internal thread 33 in the region of the nut head 44 is not completely screwed onto the screw. Specifically, the drive groove 46 of the nut will not be located above the screw at this point. Next, referring to FIG. 2, the drive nut 50 is positioned so that the protruding nips 56 are aligned and physically engaged within the drive groove 46 of the nut 40. At this point, the drive nut 50 and the nut 40 are mated, where the engagement surface 57 and the drive surface 58 of the nip 56 are in the bend 48 of the drive groove 46. . The matched drive nut 50 and nut 40 are then rotated so that the drive nut and nut are screwed onto the screw as a single unit. Once the drive nut 50 is partially screwed onto the screw 20, the drive nut and the nut are physically locked together. Next, as shown in FIG. 3, the drive nut 50 and the nut 40 are threaded onto the screw 20 until the tapered nose 42 of the nut abuts against the inner diameter 37. Next, the nut 40 is preferably subjected to a dimpling process, in which a small portion of the outer surface of the nut body 41 is physically deformed with respect to the screw 20 (not shown). ). In the recess forming process, a small portion of the nut 40 material is displaced with respect to the screw 20 to create sufficient friction to prevent loosening. The assembly process of the blind fastener 10 is then completed, and the blind fastener is ready for installation.

Installation of the assembled blind fastener 10 includes that the blind fastener 10 is used to secure a plurality of sheets or panels together. As shown in FIG. 4, the preferred installation includes two seats 12, 14 that are secured. A blind fastener 10 is inserted into the seat 12, 14, the nut head 44 being received to abut against the accessible outer surface 16 of the seat 12, and the sleeve 30 is seated 12, 14. And adjoin the inaccessible “blind” surface of the seat 14.

The installation tool (not shown) is suitable for having a custom fit with both the drive nut 50 and the machined flat portion 26 of the screw 20. The installation tool is positioned above the drive nut 50 and generates an engagement that prevents the drive nut 50 from rotating. Thus, the nut 40 also cannot rotate because the drive nut 50 and the nut 40 are mated. The installation tool also engages with the machined flats 26 of the screw 20 and provides rotational torque on the screw 20.

When the installation tool rotates the screw 20 and keeps the drive nut 50 and the nut 40 stationary, damage or chipping of the surface 43 of the nut head 44 by the drive nut 50 is prevented. It is important to note that there is no. Since there is a smooth mechanical coupling between the nip 56 of the drive nut and the mating drive groove 46 of the nut, any “jam nut effect” present in conventional blind fastener assemblies is completely eliminated. . The drive nut 50 is immutable and as a result provides consistent and predictable results. Unlike conventional blind fasteners that rely on forcing the annular ridges of the drive nut into the nut head, the drive nut 50 and the nut head 44 do not engage and deform consistently as designed when the installation load increases. Will not.

As a result of the increased installation load applied by the installation tool, the sleeve 30 is pulled toward the tapered nose 42 of the nut and the blind surface 18 of the seat 14. Referring to FIG. 5, since the sleeve 30 is made of deformable material, the sleeve body 32 and the inner diameter 37 start to expand radially when the inner diameter 37 presses on the tapered nose 42. do. The bending continues on top of the inner diameter 37 when the sleeve body 32 is adjacent to the blind face 18 of the seat 14.

At a predetermined torsional load, the sleeve 30 will deform and expand to the desired inner diameter, and the frangible groove 28 of the screw 20 will fail and break at the torsional shear. As shown, in the preferred embodiment, the frangible groove 28 is machined in an axial position on the screw 20 such that the remainder of the screw may be removed from the nut head 44 just before the soft groove 28 is broken. It is substantially coplanar with the surface 43. Moreover, the drive nut 50 can be broken together with the portion of the screw 20 that breaks with the soft groove 28 without causing any damage to the surface 43 of the nut head 44, because the nip 56 Is not deformed into the drive groove 46. As shown in Fig. 6, after the installation is completed, the seats 12, 14 are fixed together between the nut head 44 and the deformable sleeve 30. .

While the invention has been described and described in its preferred embodiments, it should be understood that changes and modifications can be made thereto and that they are within the intended full scope of the invention as claimed in the claims.

FIELD OF THE INVENTION The present invention relates to blind fasteners that hold panels and sheet materials together, and more particularly to improved drive nut assemblies.

The drive nut and assembly process of the present invention significantly improves the reliability of the blind fastener by eliminating the inconsistencies associated with forcing the drive nut into the head of the nut.

The mating connection between the drive nut and the nut head prevents damage and scratching of the nut head and preserves corrosion resistance. Unlike conventional drive nuts with deformable annular ridges, the drive nuts of the present invention do not have a "jam nut effect". The protruding nip on the drive nut eliminates the unpredictability of the installation load imposed on the screw by not forcibly deforming the nut head. This greatly reduces the risk of premature screw breakage and increases the consistency of the amount of sleeve material to be deformed with respect to the seat.

Claims (14)

A drive nut to be used in a fastener assembly, A body having a first end, a second end, and an outer surface suitable for engagement by the drive tool, A threaded bore having a plurality of internal threads extending through the body, and A plurality of protruding nips extending from the first or second ends Drive nut comprising a. The method of claim 1, And the nip has a mating surface and a driving surface suitable for engaging the groove in the fastener. The method of claim 1, The engagement surface of the nip is inclined with respect to the drive surface. The method of claim 1, The drive face of the nip is flat with respect to the drive face. The method of claim 1, At least one of said nips is square. The method of claim 1, At least one of the nips has a shape that is not rectangular. In blind fasteners, A screw having a plurality of external threads and a head located at one end of the screw, A sleeve having a plurality of internal threads and a deformable sleeve surface positioned at an end of the screw adjacent the head, A plurality of internal threads, an enlarged nut head positioned at one end of the nut, and a drive groove positioned in the enlarged nut head, the end opposite the nut head being positioned on a screw adjacent the sleeve , And And a drive nut positioned on said screw adjacent said nut, said drive nut having an outer surface suitable for engagement by a drive tool and a plurality of protruding nips extending from one end of the drive nut engaging said drive groove of said nut. The method of claim 7, wherein And a mounting tool for engaging the drive nut and screw, the installation tool holding the drive nut stationary and rotating the screw. The method of claim 7, wherein The protruding nip of the drive nut has a mating surface and a drive surface extending into the drive groove of the nut. The method of claim 9, The mating surface is an inclined blind fastener. The method of claim 7, wherein At least one of the nips of the drive nut has a rectangular configuration and the drive nut is made of a non-deformable material. The method of claim 7, wherein At least one of the nips of the drive nut has a rectangular shape and the drive groove of the nut has a geometry that allows the nip to be inserted into the drive groove. In the method of assembling the fastener system, Screwing on the screw a sleeve having a plurality of internal threads and a deformable sleeve face, Partially screwing on said screw a nut having a head having a plurality of internal threads and a drive groove; Positioning a drive nut having a plurality of internal threads and a plurality of protruding nips extending from one end of the drive nut, on the nut such that the protruding nips are aligned and mated in the drive groove of the nut; Screwing the coupled drive nut and nut onto the screw. The method of claim 13, Concave an outer surface of the nut to secure the nut on the screw.